Method for pretreating waste fat, oil and grease and co-producing first-generation biodiesel

Abstract

Provided is a method for pretreating waste fat, oil and grease (FOG) and co-producing a first-generation biodiesel, including: S1, feeding waste FOG, a liquid acid catalyst, and methanol into a pre-esterification reactor, and conducting pre-esterification to obtain a pre-esterification mixed liquid; S2, removing waste residues from the pre-esterification mixed liquid through a filter to obtain a filtrate, and separating the filtrate by a liquid-liquid separator to obtain an organic phase and an aqueous phase; S3, introducing the organic phase into a methanol recovery tower I and conducting separation to obtain a pre-esterification product and crude methanol; introducing the aqueous phase into a methanol recovery tower II and conducting another separation to obtain a liquid acid catalyst and crude methanol; S4, separating the pre-esterification product through a biodiesel refining tower to obtain a first-generation biodiesel product, and a pretreated waste FOG at a tower bottom.

1 . A method for pretreating waste fat, oil and grease (FOG) and co-producing a first-generation biodiesel, comprising:
 S1, feeding waste FOG, a liquid acid catalyst, and methanol at a certain proportion into a pre-esterification reactor, and conducting pre-esterification reaction to obtain a pre-esterification mixed liquid;   S2, removing waste residues from the pre-esterification mixed liquid after the pre-esterification reaction through a filter to obtain a filtrate, and separating the filtrate by a liquid-liquid separator to obtain an organic phase and an aqueous phase;   S3, introducing the organic phase after the pre-esterification reaction into a methanol recovery tower I and conducting separation to obtain a pre-esterification product and crude methanol; introducing the aqueous phase into a methanol recovery tower II and conducting another separation to obtain a liquid acid catalyst and crude methanol; and purifying the crude methanol through a methanol refining tower; and   S4, separating the pre-esterification product through a biodiesel refining tower to obtain a first-generation biodiesel product, and a pretreated waste FOG at a tower bottom.   
     
     
         2 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein the waste FOG in step S1 comprises one selected from the group consisting of acidified oil, hogwash oil, and swill-cooked dirty oil or a mixture thereof. 
     
     
         3 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S1, the liquid acid catalyst is a mixture of an inorganic acid and an acidic ionic liquid;
 the inorganic acid comprises one or more selected from the group consisting of concentrated sulfuric acid, phosphoric acid, and hydrochloric acid;   the acidic ionic liquid comprises one or more selected from the group consisting of an imidazolium hydrogensulfate ionic liquid, a N-alkylammonium hydrogensulfate ionic liquid, a pyridinium hydrogensulfate ionic liquid and a pyrrole hydrogensulfate ionic liquid; and   a molar ratio of the inorganic acid to the acidic ionic liquid is in a range of (0.1-0.5):1.   
     
     
         4 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S1, a molar ratio of the waste FOG to the methanol is in a range of (1-10):1, and
 a molar ratio of the liquid acid catalyst to the waste FOG is in a range of (0.01-0.1):1.   
     
     
         5 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S1, the pre-esterification reaction is conducted at a temperature of 60° C. to 120° C. and a pressure of 0.1 MPa to 1 MPa for 1 h to 10 h. 
     
     
         6 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S2, an operating temperature of the filter is in a range of 50° C. to 80° C. 
     
     
         7 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S2, the liquid-liquid separator is a chromatography device with an operating temperature of 50° C. to 80° C. and an operating time of 0.5 h to 2.0 h. 
     
     
         8 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S3, both the methanol recovery tower I and the methanol recovery tower II have an operating temperature of 60° C. to 100° C., and an operating pressure of 0.1 MPa to 1.0 MPa. 
     
     
         9 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein the methanol refining tower in step S3 is a normal-pressure fractionation tower with an operating temperature of 67° C. to 75° C. and an operating pressure of 0.1 MPa to 0.2 MP at a tower top. 
     
     
         10 . The method for pretreating the waste FOG and co-producing the first-generation biodiesel according to  claim 1 , wherein in step S4, the biodiesel refining tower is a reduced-pressure fractionation tower with an operating temperature of 100° C. to 250° C. and an operating pressure of 0.5 kPa to 2.0 kPa at a tower top.